add test for ObjectIdAutoField.deconstruct()

Author: timgraham

tests/model_fields_/test_autofield.py

@@ -4,6 +4,13 @@
 
 
 class MethodTests(SimpleTestCase):
+    def test_deconstruct(self):
+        field = ObjectIdAutoField()
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django_mongodb.fields.auto.ObjectIdAutoField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"db_column": "_id", "primary_key": True})
+
     def test_to_python(self):
         f = ObjectIdAutoField()
         self.assertEqual(f.to_python("1"), 1)